#!/usr/bin/node 
//拉取流
const Readable = require('stream').Readable;
var rs = new Readable();
//字符c，转ascii
var c = 'a'.charCodeAt(0);

rs._read = () => {
  rs.push(String.fromCharCode(c++));
  if(c > 'z'.charCodeAt(0)) {
    rs.push(null);
  }
};

rs.pipe(process.stdout);
